NPD Group today released new findings on the mobile shift, leading companies like Facebook, Google and Pandora to alter their business models as more people consume media on devices. The research firm said more than a third (37%) of those surveyed use their PC less often or not at all because they are spending more time on tablets and smartphones. Web browsing and accessing Facebook are the top activities people are switching to on mobile. The social network announced last week that 680 million of its 1 billion users now access the service via mobile, and that 23% of its ad revenue now comes from mobile. Among tablet owners, 27% say they’re using their PC less often for Web browsing, while 20% are going on Facebook less from the desktop. Similarly, 27% of smartphone owners have reduced both Internet and Facebook use on PCs in favor of their phones. Underscoring the impact of the mobile migration, Google announced Wednesday that it will soon make ad buys on tablets mandatory, even if advertisers just want to reach desktop users. With the rollout of “enhanced campaigns,” the change will go into effect for all AdWords advertisers by mid-2013. The step is expected to bolster mobile ad prices. While people are still using their computers for many PC-centric activities, NPD said tablets and smartphones are gaining ground. Internet browsing is still highest among PC owners, at 75%, followed by smartphones (61%), and tablets (53%). Facebook use follows the same pattern with PC owners at 63%, smartphone owners (55%) and tablet users (39%). TV is impacting PC usage. A fifth (21%) of consumers that have a TV connected to the Internet are now switching from their computer to using their TV to watch video from streaming services, such as Netflix, Hulu or Amazon Instant Video. Mobile devices become equipped with sharing technologies like Samsung’s AllShare and Miracast, allowing users to bridge the gap between their devices and TV screens. The NPD results were based on a survey of 4,000 U.S. adults in the fourth quarter of 2012.